Effects of ZrO2 Nanoparticles on the Microstructure and Thermal-protective Properties of PEO Coating on Al-12.5%Si Alloy

PEO ceramic coatings including ZrO 2 -Al 2 O 3 -SiO 2 in three phases were prepared on an Al- 12.5%Si alloy in electrolyte solutions containing ZrO 2 nanoparticles. The microstructures and phases of the coatings were analyzed by SEM and XRD, and the heat insulation performance and the thermal shock resistance of the coatings were investigated. The compactness of the coating increased significantly and the hindrance of the Si element on plasma electrolytic oxidation process was effectively weakened. The growth rate of the coating was improved substantially with the addition of ZrO 2 nanoparticles. The PEO ceramic coatings are primarily composed of SiO 2 and high temperature steady phases such as α-Al 2 O 3 and c -ZrO 2 . Both the content of c-ZrO 2 and the heat-insulating property of the coating increased significantly. The ceramic coatings with special microstructure and composition formed in the solutions containing ZrO 2 nanoparticles possess excellent heat insulation performance and thermal shock resistance